Owing to the trend toward broadband network development and digital technology, communication products capable of receiving and transmitting data, such as a wireless access point (AP), cellular phone, personal digital assistant (PDA), or notebook computer, are increasingly convenient, efficient, versatile, and service-oriented.
For instance, a communication product, such as a wireless network access device, usually operates in conjunction with a communication system and a wireless transmission system. The communication system comprises a central processing unit (CPU). The wireless transmission system comprises a RF module. The communication system and the wireless transmission system are installed on the same circuit board; in other words, the circuit board is capable of communication and wireless transmission.
However, with two systems sharing a circuit board, temperature of the circuit board is high, and yet dissipation of heat generated by the circuit board is hardly efficient. Hence, to optimize a design or meet other needs, it is necessary to separate the two systems. Accordingly, the communication system and the wireless transmission system are installed on different circuit boards.
With the two separate systems, the prior art discloses maintaining integrity of data by designing a layout of a circuit board as appropriate. For example, communication takes place by means of a Peripheral Component Interconnect Express (PCIe) interface provided between the communication system and the wireless transmission system. The interface is a PCIe 2.0 or 1.1 interface, and the maximum transmission speed is 2.5 Gbps. Signal distortion, crosstalk, impedance, or electromagnetic interference (EMI) become an issue to the communication system and the wireless transmission system when the systems are not installed on the same circuit board. What the PCIe interface provides is a high-speed signal crucial to quality of communication; hence, integrity of the high-speed signal is maintained on condition that differential impedance, rise time, fall time, clock, jitter, eye diagram, etc. of the high-speed signal remain unaffected.
The PCIe interface of the wireless communication system is usually provided in the form of gold fingers, which entails designing pins and slots configured for electrical connection. As a result, the designer has to allow for the space required for inserting a card into the slots, to the detriment of reduction of height, thinning of products, and dissipation of heat generated by the system.
Alternatively, coaxial cables for transmitting data between the communication system and the wireless transmission system are fit to substitute for the PCIe interfaces essential to the aforesaid layout of a circuit board. However, as prices of precious metals and raw materials are escalating in recent years, manufacturers incur high costs whenever coaxial cables are put in a checklist of procurement. Hence, at present, manufacturers do not use coaxial cables due to low industrial applicability thereof.
As explained above, the prior art is confronted with plenty problems. Accordingly, an issue that calls for immediate solution involves proposing a signal transmission technology so as to avoid problems otherwise arising from what was taught by the prior art—separation of two systems—to eliminate previous problems with the systems installed on the same circuit board.